1. Technical Field of the Invention
The present invention relates generally to electric generators. More particularly, the invention relates to a tandem alternator for a vehicle, which has a reduced axial length and an improved structure for effectively dissipating heat generated by rectifiers included therein.
2. Description of the Related Art
Japanese Patent First Publication No. H11-98789 discloses a tandem alternator for a vehicle, which includes a single rotary shaft and a front-side and a rear-side power generation unit that are arranged in tandem in the axial direction of the rotary shaft.
The tandem alternator further includes a pulley mounted on a front end portion of the rotary shaft and a first and a second rectifier that work to respectively rectify AC powers output from the front-side and rear-side power generation units into DC powers. The first and second rectifiers each generate a large amount of heat during operation of the alternator. To effectively dissipate the heat and minimize the distances from the rectifiers to the corresponding power generation units, the first and second rectifiers are respectively arranged at a front and a rear portion of the alternator.
More specifically, the tandem alternator includes a front end frame, a center frame, a housing, and a rear end frame, all of which together enclose both the front-side and rear-side power generation units. The first rectifier is fixed to an outer surface of the center frame, and is thus located inside the front frame. On the other hand, the second rectifier is fixed to an outer surface of the rear frame.
With the above arrangement, however, the total axial length of the tandem alternator is increased. This is because the first rectifier, which is interposed between the front and center frames, occupies a dedicated length in the axial direction of the rotary shaft.
Consequently, in installation of the tandem alternator to an engine of the vehicle, it may be difficult to suitably arrange the alternator without causing interference between the alternator and an inlet or exhaust pipe of the engine.
Accordingly, it is desired to reduce the axial length of the tandem alternator while securing effective dissipation of the heat generated by the first and second rectifiers.